1. Field of the Invention
The present invention relates generally to tire vulcanizing apparatus, and more particularly to a charging device for such apparatus.
2. Description of the Prior Art
The prior art vulcanizers for tire recapping are roughly classified into two types, namely one using an air bag and one using a bladder. In the air bag type, a doughnut-like air bag made of rubber and having a comparatively large wall thickness is charged into a tire to be vulcanized by using a separate charging and discharging means, then the tire with the bag in it is loaded in the vulcanizer for vulcanization with a vulcanizing medium such as steam or hot water under high pressure charged into it, and after completion of the vulcanization, the bag is removed from the vulcanized tire by using the aforementioned means again. This system requires an air bag charging and discharging unit separately of the vulcanizer, thus dictating an increase in the system's cost. In addition, the charging and discharging operations involved are rather complicated and disadvantageous from the standpoints of saving man-hours and automation.
The bladder type is an alternative one, in which a rubber bladder of a cylindrical form having a comparatively small wall thickness is provided as part of the vulcanizer. The bladder is applied over the inner surface of a tire within the vulcanizer for vulcanization with a vulcanizing medium supplied into it from its inner side, and after vulcanization it is removed out of the tire. This type of system is technologically advanced over the air bag type with respect to the saving of man-hours and facilitating the operation, and this technique is already in extensive use as a vulcanizer for new tires. However, vulcanizers for recapped tires do not usually adopt this bladder system. This is partly because of the facts that in case of a recapped tire, the percentage of use is small and also the vulcanizing plant is small in scale and less efficient in the saving of man-hours. Another ground is that in this case special technical difficulties are posed.
More particularly, in the case of recapped tires, adoption of the bladder system presents difficulties in that the distance between the upper and lower beads of a tire to be vulcanized is narrow compared to the non-vulcanized radial tire so that with the conventional vulcanizer for new tires the bladder is not smoothly applied to the inner tire surface. Accordingly, even in the presently used bladder type vulcanizer the cylindrical bladder is charged from the upper side. In this system, the state of the bladder disposed within the vulcanizer and not charged in the tire is inverted 180.degree. with respect to the state of the same bladder charged in the tire. This means that the bladder is subject to compulsive forces at the time of its charging in the tire, thus leading to short service life. Also, since the vulcanizing medium is supplied from the upper side, difficulties are involved when discharging the drainage from the bladder.